1. Field of the Invention
The present invention relates to an engine control apparatus that minimizes damage to a catalyst in a catalytic converter arranged in an exhaust passage of an internal combustion engine. More specifically, the present invention relates to an engine control apparatus that controls the fuel flow to an internal combustion engine to minimize damage to a catalyst in a catalytic converter arranged in an exhaust passage of the internal combustion engine.
2. Background Information
During deceleration of an internal combustion engine for an automobile, it has generally been practiced to cut off the fuel supply to the engine in order to improve fuel economy. However, when the supply of fuel is cut off during deceleration, the air which is sucked into the combustion chambers of the engine is expelled to the exhaust passage, and the amount of oxygen supplied to a catalytic converter midway along the exhaust passage is increased. As a result, the oxidation reaction of the uncombusted fuel inside the catalytic converter increases sharply, which causes the catalyst temperature to rise sharply. This situation may entail degradation of the performance of the catalyst and deterioration of the catalyst bed.
In this connection, an engine control apparatus is disclosed in Japanese Laid-Open Patent Publication No. 10-196433 in which the engine control apparatus controls the fuel flow to an internal combustion engine to minimize early degradation of a catalyst in a catalytic converter arranged in an exhaust passage of the internal combustion engine. This Japanese publication discloses that early degradation of the catalyst may be prevented by prohibiting the cutting of fuel flow to the engine when the temperature of the catalyst is above a prescribed temperature. This fuel cutting operation is executed when the vehicle is decelerating or when the engine is in an over speed condition, during which times it is not necessary to supply fuel to the engine. This fuel cutting operation causes an oxygen-rich lean atmosphere to occur in the exhaust system. If the fuel supply is cut while the catalyst temperature is high, the atmosphere surrounding the catalyst will become a high-temperature lean atmosphere and the catalyst will degrade early. By prohibiting the fuel cutting operation when the catalyst temperature exceeds a prescribed temperature, the catalyst is prevented from being exposed to an oxygen-rich atmosphere while at a high temperature. Thus, the catalyst is prevented from early degradation in this Japanese publication due to exposure to an oxygen-rich atmosphere while at a high temperature.
In view of the above, it will be apparent to those skilled in the art upon reading this disclosure that there exists a need for an improved engine control apparatus that minimizes damage to a catalyst in a catalytic converter arranged in an exhaust passage of an internal combustion engine. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.